Biking is a great form of aerobic exercise that will help you burn calories and lose weight. Plus, the greater your intensity--or rather, the faster you bike--the more calories you will burn. Here are some general guidelines for figuring out how many calories you will burn biking.
Running vs. biking
Although running is also a great form of aerobic exercise, the calories burnt per mile always remains the same. Two things will alter the total calories burnt---speed and weight. However, with biking there is wind resistance to add into the mix. Because of this, the faster you bike, the faster you burn not only total calories but calories per mile. Running will also give you a more intense workout, but it's easier to burn calories biking, meaning you won't have to bike as intensely as you run to burn the same number of calories.
Calories per mile
Dr. Edward Coyle at the University of Texas in Austin has worked with top athletes studying their oxygen consumption. Here is the calorie consumption he has figured out for biking:
10mph -- 0.17 calories/ Half a kilo (1 pound); 15mph -- 0.2 calories/ Half a kilo (1 pound); 20mph -- 0.25 calories/Half a kilo (1 pound); 25mph -- 0.3 calories/Half a kilo (1 pound); 30mph -- 0.38 calories/Half a kilo (1 pound);
Calculating calories per mile
To figure how many calories you will burn per mile, take your body weight and multiply it by the calorie consumption listed above for the speed at which you bike. For instance, a 64 kg (140-pound) man biking at 20mph will burn 35 calories per mile (64 Kilo x 0.25 calories/0.5kg or 1 pound), and a 72 kilo (160-pound) man biking at the same speed will burn 40 calories per mile (72 Kilogram x 0.25 calories/0.5kg or 1 pound). The heavier you are, the more calories per mile you will burn.
To calculate how many calories you burn during a bike ride, multiply the calorie factor by your weight and miles biked. For example a 68kg (150 lb.) biker, cycling 20 miles at 15 miles per hour will burn 600 calories (68 Kilogram x 20 miles x 0.2 calories/0.5kg or 1 pound).
Factors that could influence the numbers
Coyle's calculations don't take into wind and hills. Biking into a headwind will be harder than biking in a tailwind. Biking uphill will be harder than biking downhill. Also, drafting behind another rider could cut your energy needs by one-third.